High strength titanium copper alloy, manufacturing method therefor, and terminal connector using the same

ABSTRACT

A high strength titanium copper alloy consists of Ti at 2.0% by mass or more to 3.5% by mass or less; the balance of copper and inevitable impurities; an average grain size of 20 μm or less; and a 0.2% proof stress expressed by “b” of 800 N/mm 2  or more. The alloy further comprises a bending radius ratio (bending radius/sheet thickness) not causing cracking as expressed by “a” by a W-bending test in a transverse direction to a rolling direction, wherein “a” and “b” satisfy a≦0.05×b−40

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to high strength titanium copperalloys, which are superior in bending properties, used for terminalconnectors and other electronic components, a manufacturing methodtherefor, and a terminal connector using the same. The invention alsorelates to high strength titanium copper alloys, which are optimal for afork-shaped contact demanding high strength for raw material of metalmaterial, a manufacturing method therefor, and a fork-shaped connectorusing the titanium copper alloy.

[0003] 2. Description of the Related Art

[0004] Copper alloy containing titanium such as C1990 (hereinaftercalled titanium copper alloy) is noted for its superior workability andmechanical strength, and is widely used in terminal connectors and inother applications for electronic components. On the other hand, thetrend toward miniaturization of electronic components is recentlystronger than before, and the wrought product of copper alloys forelectronic components are required to be even thinner in thickness tocope with this trend. In a view of the thinness of material, higherstrength of the material itself is required to maintain the contactpressure of the connector, and a small bending radius is required in thebending process of components to fulfil the function in a limited space.That is, the titanium copper alloy is required to have contrarycharacteristics of high electrical conductivity and high strength andsuperior bending properties.

[0005] Furthermore, along with the advancement in high density mountingsfor cellular phones, digital cameras, video cameras, etc., metal membersfor electronic components such as terminal connectors and lead framesare bent and formed in very complicated shapes, and an superior bendingproperties is required, in particular, in addition to having highstrength.

[0006] Under such circumstances, in order to improve bending propertiesand the stress relief rate of the titanium copper alloy, much has beenreported about the manufacturing method of solution treatment ofcrystals, under heat treatment condition, not exceeding a grain size of20 μm (for example, Japanese Patent Application Laid-Open No. 7-258803).However, to satisfy the requirement of bending properties of the copperalloy material used in recent electronic components such as terminalconnectors, at present, such an improved titanium copper alloy does nothave sufficient bending properties. To satisfy the requirements fortitanium copper alloy, it is important to improve the correlation ofstrength and bending properties, and for this purpose, it is alsonecessary to improve the manufacturing method for titanium copper alloy.

[0007] Hitherto, where the required tensile strength of copper alloy forelectronic component was at a medium level of about 500 to 800 MPa,brass, phosphor bronze, or nickel silver is used, or where a higherelectrical conductivity is required, Cu—Ni—Si, Cu—Cr—Zr, or Cu—Cr—Sncopper alloy is used, and where a high strength over about 900 MPa isrequired, beryllium copper or titanium copper is used.

[0008] Recently, demand for FPCs (flexible printed circuit boards) isincreasing, and the connectors for FPCs are modified. The fork-shapedconnector is used in a connector for an FPC, and in contrast to thegeneral-purpose connector used on the surface contacting with metalmaterial, it is designed to contact with the circuit board on thefracture of the copper alloy plate. Accordingly, a bending process isnot necessary, and the fork-shaped connector is required to have a highstrength, in the first place, if the bending properties are notfavorable.

[0009] Specifically, the fork-shaped connector is required to have atensile strength of at least 1000 MPa or more, and in order to beapplicable to versatile designs, a tensile strength of 1200 MPa or moreis necessary.

[0010] Stainless steel of high strength, for example, SUS301 has atensile strength exceeding 1200 MPa, but stainless steel is low inelectrical conductivity, about 2.4% IACS, and cannot be used for afork-shaped connector. A fork-shaped connector is required to have anelectrical conductivity of at least 10% IACS.

[0011] As a copper alloy having a tensile strength of 1200 MPa or more,beryllium copper is well known. As a high strength copper alloy,titanium copper is also usable, but in order to have a tensile strengthof 1200 MPa or more, titanium must be contained at 4% by mass, and itfurther requires special treatment such as MTH (aging, working, heating)(Lecture on Modem Metal Materials 5, Nonferrous Materials, p. 78 (JapanSociety of Metallurgy), etc.).

[0012] However, titanium copper containing Ti at 4% by mass is poor inworkability, and is likely to crack in hot rolling or to develop edgecracks in cold rolling, and it is difficult to manufacture at high proofstress industrially, and it is also difficult to sell commercially asmaterial for electronic components. The MTH treatment is a process ofcold rolling of titanium copper after aging, followed by heat treatment,but cold rolling of titanium copper alloy after aging is likely to causeedge cracking, and it is difficult to manufacture.

[0013] On the other hand, in the conventional manufacturing method fortitanium copper containing 3% by mass of Ti (Cl990), the obtainedtensile strength is about 1000 MPa at most. Japanese Patent ApplicationLaid-Open No. 7-258803 discloses a manufacturing method of solutiontreatment of titanium copper alloy in the heat treating condition inwhich the crystal grain does not exceed 20 μm, and it is known that amaterial which is superior in bending properties and is not lowered instrength can be manufactured as compared with similar conventionalmaterials; however, titanium copper of high strength is not obtainable.Therefore, as a copper alloy having a tensile strength of 1200 MPa,there was no copper alloy other than beryllium copper, which monopolizedthe market.

[0014] However, beryllium copper is not an ideal copper alloy; it isinferior to titanium copper in stress relief characteristics, and is notfully satisfactory. Therefore, in a titanium copper alloy containing Tiat 2.0 to 3.5% by mass, if the tensile strength could be improved to1200 MPa or more, the alloy would be an optimal high strength copperalloy having the stress relief characteristics, and hence improvement isanticipated.

SUMMARY OF THE INVENTION

[0015] The invention is made in light of above circumstances, and it ishence an object thereof to provide a titanium copper alloy as a terminalconnector material which is enhanced in strength without having loweredbending properties. It is also an object of the invention to provide ahigh strength titanium copper alloy having a tensile strength of 1200MPa or more, equivalent to that of beryllium copper, and an electricalconductivity of 10% IACS or more, a manufacturing method thereof, and anelectronic component using the same high strength titanium copper alloy,in particular, a fork-shaped connector.

[0016] The inventors attempted to adjust conditions of the finalrecrystallization annealing of titanium copper alloy (conditions ofsolution treatment), and the subsequent cold rolling and agingconditions, researched the relationship between characteristic valuesafter final heat treatment, and discovered that a titanium copper alloymaterial enhanced in strength without having lowered bending propertiescan be obtained stably.

[0017] The present invention is made on the basis of the aboveknowledge. A first aspect of the present invention provides a highstrength titanium copper alloy consisting of Ti at 2.0% by mass or moreto 3.5% by mass or less; the balance of copper and inevitableimpurities; and an average grain size of 20 μm or less; the alloyfurther comprising a 0.2% proof stress expressed by “b” of 800 N/mm² ormore; and a bending radius ratio (bending radius/sheet thickness) notcausing cracking as expressed by “a” by a W-bending test in a transversedirection to a rolling direction; wherein “a” and “b” satisfya≦0.05×b−40.

[0018] The second aspect of the invention provides a high strengthtitanium copper alloy consisting of Ti at 2.0% by mass or more to 3.5%by mass or less; at least one of Zn, Cr, Zr, Fe, Ni, Sn, In, Mn, P, andSi at 0.01% by mass or more to 3.0% by mass or less in total; and thebalance of copper and inevitable impurities; the alloy furthercomprising an average grain size of 20 μm or less; a 0.2% proof stressexpressed by “b” of 800 N/mm² or more; and a bending radius ratio(bending radius/sheet thickness) not causing cracking as expressed by“a” by a W-bending test in a transverse direction to a rollingdirection; wherein “a” and “b” satisfy a≦0.05×b−40.

[0019] The reasons for setting the numerical values specified above areexplained below together with the operation of the invention. In thefollowing explanation, “%” means “% by mass.”

[0020] A. Ti: 2.0 to 3.5%

[0021] Ti is characterized by inducing spinodal decomposition by agingof Cu—Ti alloy, thereby generating a concentration modulation structurein the matrix, and assuring a very high strength. However, desiredreinforcement is not expected if the content is less than 2.0%. If Ti iscontained at more than 3.5%, precipitation of grain boundary reactiontype is likely to occur, and the strength may be lowered, in contrast,and the workability deteriorates. Hence, the content of Ti is defined ina range of 2.0to 3.5%.

[0022] B. Zn, Cr, Zr, Fe, Ni, Sn, In, Mn, P, Si: 0.01 to 3.0% in Total

[0023] Cr, Zr, Fe, Ni, Sn, In, Mn, P, and Si are all known to suppressprecipitation of grain boundary reaction type without substantiallylowering the electrical conductivity of a Cu—Ti alloy, make grain sizefine, and increase the strength by aging precipitation. Moreover, Sn,In, Mn, P, and Si are known to increase the strength of a Cu—Ti alloy bysolid solution reinforcement. Therefore, one or more elements thereofare added as required. However, if the total content thereof is lessthan 0.01%, desired effects are not expected. If the total contentexceeds 3.0%, the electrical conductivity and workability of the Cu—Tialloy deteriorate significantly. Therefore, the content of one elementor more elements of Zn, Cr, Zr, Fe, Ni, Sn, In, Mn, P, and Si isspecified to be in a range of 0.01 to 3.0% in total.

[0024] Of these additive elements, Zn is expected to suppress heat peeloff of solder without lowering the electrical conductivity of a Cu—Tialloy, and is added most preferably. However, if the content of Zn isless than 0.05%, desired effects are not expected. If the content of Znexceeds 2.0%, the electrical conductivity and stress reliefcharacteristics deteriorate. Therefore, the content of Zn is preferredto be in a range of 0.05 to 2.0%.

[0025] C. Characteristics of Titanium Copper Alloy

[0026] In order that a titanium copper alloy be used as a terminalconnector material, in particular, the bending properties are importantbecause it is used being formed into a complicated part, together withits material strength. In the designing of a part, considerations aregiven to the 0.2% proof stress as the index of material strength, andthe bending properties evaluated by the state of the bending part whenit is bent at various bending radii with respect to the material platethickness. The inventors quantitatively analyzed the bending propertiesdepending on the strength and plate thickness required in the recentelectronic components, and discovered a specific scale balancing both asexplained below.

[0027] That is, when the 0.2% proof stress expressed by “b” is 800 N/mm²or more, the bending radius ratio (bending radius/sheet thickness) notcausing cracking as expressed by “a” by a W-bending test in a transversedirection to a rolling direction, “a” and “b” satisfy a≦0.05×b−40, thehigh strength and bending properties can be balanced, and the titaniumcopper alloy can meet recent demands. The 0.2% proof stress of titaniumcopper alloy is defined to be 800 N/mm² or more because the highstrength characteristics as a titanium copper alloy cannot be exhibitedsufficiently if less than 800 N/mm². In the invention, the grain size ismeasured by using the value obtained by the cutting method according toJIS H 0501.

[0028] To enhance the strength of titanium copper alloy, it has beenknown to reinforce the solid solution by adding alloy elements,reinforce precipitation by adequately controlling the aging temperature,or reinforce by work hardening by adequately controlling the workingratio before aging, and hitherto the desired material characteristicswere assured by combining these methods. However, when the strength isenhanced by such reinforcing mechanisms only, the bending properties maydeteriorate, and it may fail to reach a desired region of materialcharacteristics. Accordingly, the inventors conducted various tests, andfound that there is a relationship between the strength and bendingproperties with respect to the grain size, and that the average grainsize of 20 μm is required in order to obtain the above relationship of0.2% proof stress and bending radius ratio.

[0029] Furthermore, in order to enhance the bending properties withoutlowering the material strength, it is necessary to define the grain sizestrictly, and to control adequately the final recrystallizationannealing condition, cold working ratio, and aging temperature. Theinvention also provides a terminal connector using such titanium copperalloy.

[0030] The manufacturing method for titanium copper alloy of theinvention is characterized by performing final recrystallizationannealing at a temperature below the borderline L of the α-phase and theα+Cu₃Ti phase shown in FIG. 1.

[0031] It is essential in the invention to specify the finalrecrystallization annealing condition, and the subsequent cold workingand aging conditions. The final recrystallization annealing condition isintended to facilitate the subsequent process, and to adjust thematerial characteristics and grain size.

[0032] Hitherto, to manufacture a titanium copper alloy of which thegrain size does not exceed 20 μm, the grain size was adjusted byadequately controlling the treatment time by determining the treatingtemperature in a solid solution region of Ti. However, in the case ofrecrystallization by solution treatment at high temperature and in ashort time, since the uniformity of grain size is insufficient, althoughthe strength may be enhanced, the workability is impaired, thecharacteristics vary widely, and hence it was difficult to stabilize thehigh strength of titanium copper alloy at a grain size of 20 μm or less.

[0033] Accordingly, the inventors made various tests aboutrecrystallization annealing, and discovered that a titanium copper alloysuperior in bending properties without lowering the strength and havingsmall variations of characteristics can be obtained, in eachcomposition, by performing recrystallization annealing at a temperaturebelow the borderline L of α−(α+Cu₃Ti) which is the borderline of thesolid solution-precipitation, that is, in a temperature region partiallycausing precipitation, instead of temperature region of solid solutionof all contained Ti in Cu, for a time so that the average grain sizedoes not exceed 20 μm. The temperature y (° C.) of α−(α+Cu₃Ti)borderline L can be approximated in formula y=50x+650, where x (%) isthe concentration of Ti.

[0034] Meanwhile, as the grain size becomes finer, the bendingproperties are better, but if the average grain size is less than 3 μm,non-recrystallized portion may remain, and the bending properties maydeteriorate, and therefore the average grain size should be 20 μm orless, more preferably 3 to 20 μm.

[0035] The cooling rate after recrystallization annealing should be 100°C./sec or more. If the cooling rate is less than 100° C./sec, spinodaldecomposition occurs at the time of cooling, and the material ishardened, and the subsequent working becomes difficult. It is hencepreferred to cool the material surface coming out of the heating furnaceby water or steam and water, so that the material can be cooleduniformly while maintaining the specified cooling rate.

[0036] Furthermore, in order to obtain such characteristics correlationof 0.2% proof stress and bending properties, aside from therecrystallization annealing condition, it is required to specify thesubsequent cold working ratio and aging condition strictly. Afterrecrystallization annealing, almost all Ti of the material is in solidsolution, and then it is worked by cold rolling and aged. The workingratio of cold rolling is preferred to be 5 to 70% or less. If it is lessthan 5%, increase in strength by work hardening is small, and desiredstrength is not obtained, but when the working ratio exceeds 70%,although a high strength is obtained by adequately controlling the agingcondition, the bending properties deteriorate, and the correlation of0.2% proof stress and bending properties are not obtained.

[0037] The aging condition is preferred to be 300° C. or more to 600° C.or less. If the aging temperature is less than 300° C., aging is notsufficient, and the material strength is not improved. If it is aged ata temperature over 600° C., the solid solution amount of Ti is excessive(the precipitation amount is less), and desired strength is notobtained. The period of aging is preferred to be 1 hour or more to 15hours or less. If it is less than 1 hour, improvement of strength andelectrical conductivity by aging is not expected, or if it exceeds 15hours, the strength declines due to over-aging.

[0038] Accordingly, the titanium copper alloy of the invention is anaging-cured type copper alloy of superior bending properties and highstrength, and it is used in the terminal connector of small size inwhich superior bending properties and high strength are required. If thecontact of the terminal connector is plated before or after pressworking, the strength and bending properties hardly deteriorate, and theeffect of the invention is exhibited.

[0039] Such high strength titanium is generally press worked after theaging process. The inventors discovered that the bending properties arefurther enhanced by limiting the range of grain size in further narrowerbounds while aging after pressing process. That is, the inventionaccording to a third aspect provides a titanium copper alloy which issubjected to an aging process after press working, the alloy consistingof: Ti at 2.0% by mass or more to 3.5% by mass or less; and the balanceof copper and inevitable impurities; the alloy further comprising agrain size of 5 to 15 μm; wherein cracking does not occur by a W-bendingtest in a transverse direction to a rolling direction with a bendingradius of zero before the aging process, and the hardness of the workedmatrix after the aging process is 300 Hv or more, and it is morepreferable that it be 310 Hv or more.

[0040] Moreover, the invention according to a fourth aspect provides atitanium copper alloy which is subjected to an aging process after pressworking, the alloy consisting of: Ti at 2.0% by mass or more to 3.5% bymass or less; at least one of Zn, Cr, Zr, Fe, Ni, Sn, In, Mn, P, and Siat 0.01% by mass or more to 3.0% by mass or less in total; and thebalance of copper and inevitable impurities; the alloy furthercomprising a grain size of 5 to 15 μm; wherein cracking does not occurby a W-bending test in a transverse direction to a rolling directionwith a bending radius of zero before the aging process, and the hardnessof the worked matrix after the aging process is 300 Hv or more, and itis more preferable that it be 310 Hv or more.

[0041] Such high strength titanium copper alloy is manufactured byperforming final recrystallization annealing at a temperature below theborderline of α-phase and α+Cu₃Ti phase to adjust the grain size to 5 to15 μm, and executing final cold rolling at a working ratio of 5 to 50%.The aging conditions may be the same as in the first and second aspectsof the invention, and such a manufacturing method is also one of thefeatures of the invention. Furthermore, the third and fourth aspects arealso applied in the terminal connector of small size where superiorbending properties and high strength are required, and such a terminalconnector is also one of the features of the invention.

[0042] The inventors further researched the manufacturing process oftitanium copper alloy, and adjusted the hot rolling condition, and thesubsequent cold rolling condition and aging condition, and discoveredthat a high strength titanium copper alloy having a tensile strength of1200 MPa or more can be obtained stably.

[0043] That is, a fifth aspect of the invention provides a high strengthtitanium copper alloy consisting of: Ti at 2.0% by mass or more to 3.5%by mass or less; and the balance of copper and inevitable impurities;the alloy further comprising a tensile strength of 1200 MPa or more andan electrical conductivity of 10% IACS or more.

[0044] The sixth aspect of the invention provides a high strengthtitanium copper alloy consisting of: Ti at 2.0% by mass or more to 3.5%by mass or less; Zn at 0.05% by mass or more to 2.0% by mass or less; atleast one of Cr, Zr, Fe, Ni, Sn, In, Mn, P, and Si at 0.01% by mass ormore to 3.0% by mass or less in total; and the balance of copper andinevitable impurities; the alloy further comprising a tensile strengthof 1200 MPa or more and an electrical conductivity of 10% IACS or more.

[0045] The high strength titanium copper alloy can be manufactured byhot rolling at a temperature of 600° C. or more, cold rollingsuccessively at a working ratio of 95% or more, and aging at temperatureof 340° C. or more to less than 480° C. for 1 hour or more to less than15 hours while maintaining the state of the matrix after cold rolling.

[0046] The invention further provides a fork-shaped connector using thehigh strength titanium copper alloy of the fifth or sixth aspect.

[0047] In the fifth and sixth aspects, the reasons for limiting thecontents are the same as in the first and second aspects. The reasonsfor limiting the characteristic values in the fifth and sixth aspectsare as follows.

[0048] (1) Tensile Strength

[0049] The fork-shaped connector for FPC differs from thegeneral-purpose connector contacting with the surface of metal material,is designed to contact with the circuit board at the fracture of copperalloy plate, and is not processed by bending. Accordingly, therequirement of prime importance is the strength. In the invention, thestrength is evaluated by tensile strength. The required tensile strengthof a fork-shaped connector is not sufficient at the tensile strengthobtained by general-purpose copper alloy such as brass, phosphor bronze,or nickel silver, but is 1200 MPa or more so as to be applicable toversatile designs as fork-shaped connectors.

[0050] (2) Electrical Conductivity

[0051] As the metal material for fork-shaped connector for FPC, thestrength is most important, but since the fork-shaped connector isdesigned to contact at the fracture of metal material, the contactresistance is larger than in other connectors. As a countermeasure, thecontact area is plated with gold, but certain electrical conductivity isalso required as metal material. Some stainless steel materials are highin strength, but the electrical conductivity is low, and the heatgenerated in the contact portion is poorly dissipated. At least, anelectrical conductivity of 10% IACS is needed.

[0052] The high strength titanium copper alloy of the fifth and sixthaspects is manufactured in the following method.

[0053] Hitherto, in the manufacturing method for enhancing the strengthof titanium copper alloy, after hot rolling, cold rolling and heattreatment, the material is heated (solution treatment) to adjust thegrain size at 20 μm or less, and the working ratio of final cold rollingand aging temperature are properly controlled, so that a material oftensile strength of about 1000 MPa and superior bending property ismanufactured (Japanese Patent Application Laid-Open No. 7-258803).However, considering the manufacturing efficiency, in the Ti amountrange of 2.0 to 3.5% by mass, the tensile strength of 1200 MPa or moreis not yet achieved in the high strength titanium copper alloymanufactured in this method. As for the MTH treatment mentioned above,the tensile strength of 1200 MPa or more is not yet obtained in the Tiamount range of 2.0 to 3.5% by mass.

[0054] In the manufacturing method of the invention, it is essential tospecify the “material temperature in hot rolling,” “working ratio incold rolling before aging process,” and “aging condition.”

[0055] (1) Hot Rolling

[0056] Hot rolling is intended to homogenize the cast matrix, and toinduce dynamic recrystallization by rolling at higher temperature, sothat subsequent processes can be easily performed. If the materialtemperature is lower than 600° C. during hot rolling, titanium copperalloy causes spinodal decomposition to harden abruptly, and thesubsequent cold working is difficult, and the characteristics varywidely. Therefore, the material temperature is kept above 600° C. duringthe hot rolling process. As for cooling after hot rolling, the materialhardness unless cooled quickly and the subsequent rolling is difficult,and therefore, by water cooling or the like, the cooling rate of thematerial is preferred to be 200° C./sec or more.

[0057] (2) Cold Rolling

[0058] So far, the titanium copper alloy was cold rolled and annealedafter the hot rolling process, and then cold rolled to a specified sheetthickness, and was further heated (solution treatment) for a short timeat a high temperature before aging process. That is, heat treatment isintended to adjust the material characteristics and to make thesubsequent processing easier, but since the heat treatment is appliedbetween the hot rolling and the aging, a proper working ratio of coldrolling cannot be set, the strength is lowered, and it is hard to obtaina desired high strength.

[0059] However, by strictly specifying the working condition of hotrolling, a strong working of 95% or more is possible in the subsequentcold rolling. Herein, the working ratio of cold rolling is 95% or morebecause the working ratio must be specified strictly in order to obtaina tensile strength of 1200 MPa or more by the subsequent aging process,although the strength is generally elevated as the working ratio ishigher, and a tensile strength of 1200 MPa or more can be obtained bydefining the working ratio at 95% or more.

[0060] (3) Aging

[0061] After the cold rolling process, the material is aged in order toreinforce the strength and improve the elongation, elastic property andelectrical conductivity. The aging temperature is defined in a range of340° C. to less than 480° C., that is, if the aging temperature is lessthan 340° C., the aging effect is not sufficient, and the strength andelectrical conductivity are not improved, but at 480° C. or more, sincethe cold rolling working ratio before aging process is strong working of95% or more, it may result in over-aging if aged for a short time, andthe strength is lowered and desired characteristics are not obtained,and therefore the temperature range of 340° C. or more to less than 480°C. is specified.

[0062] The aging period is 1 hour or more to less than 15 hours, thatis, if less than 1 hour, improvement of strength and electricalconductivity by aging is not expected, and if 15 hours or more, thestrength is lowered due to excessive over-aging, and hence the agingperiod is defined in a range of 1 hour or more to less than 15 hours.

[0063] Such high strength titanium copper is generally press workedafter the aging process. The inventors discovered that dimensionalchanges after aging are substantially small. Therefore, the inventionaccording to a seventh aspect provides to a titanium copper alloy whichis subjected to an aging process after press working, the alloyconsisting of: Ti at 2.0% by mass or more to 3.5% by mass or less; andthe balance of copper and inevitable impurities; the alloy furthercomprising a worked matrix having a hardness of 345 Hv or more after theaging process.

[0064] Furthermore, an eighth aspect of the invention provides atitanium copper alloy which is subjected to an aging process after pressworking, the alloy consisting of: Ti at 2.0% by mass or more to 3.5% bymass or less; Zn at 0.05% by mass or more to 2.0% by mass or less; atleast one of Cr, Zr, Fe, Ni, Sn, In, Mn, P, and Si at 0.01% by mass ormore to 3.0% by mass or less in total; and the balance of copper andinevitable impurities; the alloy further comprising a worked matrixhaving a hardness of 345 Hv or more after the aging process.

[0065] The high strength titanium copper alloys of the seventh andeighth aspects are manufactured by hot rolling at a temperature of 600°C. or more, and cold rolling successively at a working ratio of 95% ormore, and such a manufacturing method is also one of the features of theinvention. The high strength titanium copper alloys of the seventh andeighth aspects are particularly suited to a fork-shaped connector, andsuch a fork-shaped connector is also one of the features of theinvention.

BRIEF DESCRIPTION OF DRAWING

[0066]FIG. 1 is a Ti—Cu equilibrium diagram.

DESCRIPTION OF THE PREFERRED EMBODIMENTS EXAMPLES Example 1

[0067] The invention is specifically explained below by referring toexample 1 which shows a particularly preferred alloy composition range.First, using electrolytic cathode copper or oxygen-free copper as a rawmaterial, copper alloy ingots (50 mm thick×100 mm wide×200 mm long) ofvarious compositions shown in Table 1 (examples) and Table 2(comparative examples) were melted in a high frequency melting furnace.Consequently, each ingot was heated for 1 hour at a temperature of 850to 950° C., and was hot rolled, and a plate with 8 mm thick wasobtained. At this time, the material temperature after hot rolling was650° C. or more, and the material was cooled in water after hot rolling.The oxide layer on the surface of the sheet was polished and removed,and rolling and recrystallization annealing were repeated, and afterproper pickling, recrystallization annealing (solution treatment) wasconducted in the condition of Tables 1 and 2, being followed by coldrolling and aging, and a material having a thickness of 0.2 mm wasobtained. After recrystallization annealing, the material was cooled byimmersing in water after heat treatment. At this time, the cooling ratewas 200° C./sec or more, which was confirmed by attaching a thermocoupleto the material surface. The table also records the value of temperatureof α−(α+Cu₃Ti) borderline as approximated in formula (y=50x+650). Asshown in Table 1, in the invention, recrystallization annealing wasconducted at a temperature below the α−(α+Cu₃Ti) borderline and within50° C. TABLE 1 Manufacturing conditions Recrystallization annealingcondition Aging condition Composition Temperature at Average crystalCold rolling Heating Holding (unit: % by mass) α−(α + Cu₃Ti) Temperatureparticle size processing ratio temperature time No. Ti Others borderline(° C.) (° C.) (μm) (%) (° C.) (hours) 1 3.2 — 810 770 10 50 380 6 2 2.9— 795 750 5 40 400 6 3 2.6 — 780 750 5 40 420 6 4 2.4 — 770 750 5 40 4206 5 3.5 — 825 770 10 50 400 6 6 3.0 — 800 770 10 50 400 6 7 2.9 Zn1.0795 750 10 50 380 10 8 2.2 Sn0.21 760 750 10 30 380 10 9 2.5 Cr0.10 775750 10 65 380 6 10 3.0 Zr0.15 800 770 10 60 380 6 11 3.2 Fe0.20 810 7505 50 400 6 12 2.7 Ni0.30 785 750 10 50 380 6 13 3.2 In0.25 810 770 5 40420 6 14 3.0 Mn0.10 800 750 10 50 380 10 15 3.1 P0.07 805 750 5 50 40010 16 2.8 Si0.13 790 750 10 30 380 6 17 2.7 Zn0.70, 785 750 5 60 380 6Cr0.30, Zr0.15 18 2.7 Zn0.50, 785 750 10 60 420 6 Fe0.15, P0.05 19 2.9Zn1.2, 795 750 5 30 420 6 In0.10, Fe0.16, P0.03 20 3.1 Sn0.15, 805 77010 50 400 6 P0.15 21 2.6 Mn0.15 780 750 10 60 380 6 P0.10 22 2.9 Zn0.80,795 750 10 60 380 6 Ni0.25, Si0.05 23 3.3 Zn1.1, 815 770 10 60 380 6Cr0.15, Zr0.05, Mn0.05 24 3.2 Zn0.1, 810 770 10 60 380 6 Ni0.25, Sn0.15

[0068] TABLE 2 Manufacturing conditions Recrystallization annealingcondition Aging condition Composition Temperature at Average crystalCold rolling Heating Holding (unit: % by mass) α−(α + Cu₃Ti) Temperatureparticle size processing ratio temperature time No. Ti Others borderline(° C.) (° C.) (μm) (%) (° C.) (hours) 25 1.0 — 700 680 5 50 400 6 26 1.7— 735 700 5 50 380 6 27 5.5 Ni0.50, 925 770 10 40 450 6 P0.15 28 4.5Zn0.50, 875 770 10 40 400 6 Ni1.20, Sn0.50 29 2.8 Zn4.2, 790 750 10 40380 6 Ni1.30, Si0.40 30 3.1 Zn1.5, 805 750 5 50 380 10 Ni1.50, Sn1.10,P0.30 31 3.0 — 800 810 25 50 380 6 32 2.9 — 795 850 30 60 380 6 33 3.2 —810 750 10 80 360 2 34 2.7 Zn1.0, 785 750 10 90 360 2 In0.30, P0.15 353.1 Zn1.5, 805 750 5 60 200 6 Fe0.35, Mn0.15 36 3.1 Zn1.8, 805 750 10 50450 50 Sn0.50 37 3.0 — 800 770 10 50 650 0.5 38 2.9 — 795 750 10 40 4500.5 39 2.8 — 790 750 5 50 200 50

[0069] From these materials obtained by such series of processing,various test pieces were sampled, and the characteristics thereof weretested. First, to evaluate the elastic properties and strength, tensiletests were conducted, and 0.2% proof stress, tensile strength andelongation were measured according to JIS Z 2201 and Z 2241. As forbending properties, test pieces measuring 10 mm wide×100 mm long weresampled at the transverse angle to the rolling direction, and W-bendingtests (JIS H 3110) were conducted at various bending radii, and theminimum bending radius ratio (r/t, r: bending radius, t: test piecethickness (sheet thickness)), not causing cracking, capable of obtaininga favorable bend appearance of rank C or higher in the evaluationstandard according to Japan Brass Technical Association standard JBTAT307: 1999 was determined by observing the bend with an opticalmicroscope. This evaluation standard is classified in five ranks; rankA: no wrinkle, rank B: small wrinkle, rank C: large wrinkle, rank D:small crack, and rank E: large crack, and in the case of bending test atlarger bending radius ratio than the bending radius ratio for obtainingthe result of rank C, appearance of the same or better ranks A to C isobtained. In W-bending test, the bending axis is parallel (Bad Way) tothe rolling direction in which the bending properties are inferior. Thebending radius is the distance from the center of bending to the innercircumference of the test piece, and the results were evaluated by usinga tool having various bending radii.

[0070] Results of characteristic tests are shown in Table 3 (examples)and Table 4 (comparative examples). In examples No. 1 to No. 24, thebending radius ratio (bending radius/sheet thickness) not causing crackas expressed by “a” and 0.2% proof stress expressed by “b”, and “a” and“b” satisfy the relationship “a≦0.05×b−40”, and the titanium copperalloy (evaluation: favorable) meeting the recent demands, andwell-balanced between high strength and bending properties, could beobtained. In contrast, in comparative examples No. 25 to No. 39, asexplained below, the requirements of the invention were not satisfied,and poor bending properties and other problems were found at 0.2% proofstress.

[0071] In No. 25 and 26, since the Ti content is low, high strength of0.2% proof stress of 800 N/mm² or more is not obtained. In No. 27 and28, the strength is lower than in the alloy of the example of theinvention, and the bending radius ratio is large, and the bendingproperties are poor. This is because the Ti content is too high, andthere is too much precipitation into the grain boundary not contributingto enhancement of strength, and it seems cracks are initiated from theprecipitates in the grain boundary at the time of performing tensiontests and bending tests.

[0072] No. 29 has too high amount of Zn, and No. 30 has too high a totalamount of subsidiary additives, and they are both low in electricalconductivity and poor in bending properties. No. 31 and 32 are examplesof extremely high recrystallization temperature, in which average grainsize of 20 ,m or less was not obtained, and high 0.2% proof stress couldnot be obtained. When compared with an alloy example of 0.2% proofstress of the same level in the invention, the bending radius ratio islarge and bending properties are poor. No. 31 is a mixed grain matrix.Accordingly, the average grain size in No. 31 is 25 μm, being smallerthan in No. 32, but the bending radius ratio varied in a range of 3.0 to5.0. The maximum value is recorded in Table 4.

[0073] No. 33 and 34 are examples of too high working ratio of coldrolling, but by shortening the aging period, a high 0.2% proof stresswas obtained, however, the bending properties were poor. No. 35 is anexample of low aging temperature, and since the temperature is low, theaging effect is insufficient, and the strength is low. No. 36 is anexample of too long aging period, and 0.2% proof stress is lowered dueto over-aging.

[0074] No. 37 is an example of too high aging temperature and too shortaging period, and since the aging temperature is too high, the solidsolution amount of Ti is excessive, and since the aging period is short,sufficient 0.2% proof stress is not obtained. No. 38 is an example ofshort aging period, and the aging effect is insufficient, and the 0.2%proof stress is low. No. 39 is an example of low aging temperature, andin spite of long aging period of 50 hours, high 0.2% proof stress is notobtained.

[0075] Therefore, in the alloy examples of the invention, byrecrystallization annealing (solution treatment) at a temperature belowthe α−(α+Cu₃Ti) borderline in an appropriate composition, and performingthe subsequent cold rolling and aging process in adequate conditions, afavorable relation of 0.2% proof stress and bending radius ratio isobtained, and titanium copper alloy of high strength is obtained withoutsacrificing the bending properties. In contrast, in alloys ofcomparative examples, as compared with alloys of the invention,favorable relation of 0.2% proof stress and bending radius ratio is notobtained, and material with good balance is not produced. TABLE 3Tensile 0.2% proof Bending radius Electrical strength stress (b)Elongation ratio Conductivity No. (N/mm²) (N/mm²) (%) 0.05 × b-40 (r/t)(%IACS) 1 1050 900 15 5.0 3.0 14.4 2 1030 880 17 4.0 2.0 14.3 3 1030 90015 5.0 2.0 14.1 4 1020 900 16 5.0 2.0 14.3 5 1050 940 15 7.0 3.0 13.6 61070 960 14 8.0 3.0 13.2 7 1030 890 17 4.5 3.0 14.2 8 880 830 23 1.5 1.015.3 9 970 880 18 4.0 3.0 13.4 10 1010 900 17 5.0 3.0 14.4 11 1060 92017 6.0 3.0 14.5 12 1030 910 15 5.5 3.0 14.5 13 1070 930 10 6.5 4.0 13.414 1040 910 15 5.5 3.0 13.4 15 1040 920 14 6.0 3.0 13.7 16 950 850 202.5 0.0 13.5 17 1110 950 8 7.5 4.0 14.7 18 1010 900 14 5.0 3.0 14.0 19970 860 18 3.0 1.0 15.1 20 1060 940 10 7.0 3.0 14.0 21 990 900 12 5.04.0 14.4 22 1050 930 11 6.5 3.0 13.7 23 1080 990 8 9.5 4.0 14.7 24 1040930 11 6.5 4.0 14.6

[0076] TABLE 4 Tensile 0.2% proof Bending radius Electrical strengthstress (b) Elongation ratio Conductivity No. (N/mm²) (N/mm²) (%) 0.05 ×b-40 (r/t) (%IACS) 25 680 600 11 — 5.0 35.0 26 790 710 8 — 5.0 20.3 27750 720 1 — 8.0 10.4 28 800 750 2 — 7.0 10.3 29 960 860 8 3.0 5.0 8.3 30950 840 10 2.0 5.0 7.1 31 850 760 25 — 5.0 14.3 32 880 800 20 0.0 4.014.4 33 1150 970 10 8.5 >10.0 15.3 34 1180 990 15 9.5 >10.0 15.1 35 820750 3 — 3.0 12.1 36 890 780 20 — 3.0 15.2 37 800 720 18 — 1.0 15.1 38850 760 7 — 4.0 12.3 39 820 750 7 — 3.0 12.4

Example 2

[0077] Test pieces were press worked at the process conducted up to coldrolling in the same condition as in examples No. 2 and No. 10 in example1 except that the final recrystallization annealing was conducted in theconditions as shown in Table 5. The press worked test pieces wereevaluated by W-bending test in the same condition as in example 1, andthen were subjected to aging. The aging conditions were 400° C. and 6hours in No. 2, and 380° C. and 6 hours in No. 10. Before and after theaging process, characteristics of test pieces were examined using thesame method as in example 1, and the results are shown in Table 5. As isclear from Table 5, when the average grain size is in a range of 5 to 15μm, the bending radius ratio (r/t) is zero, and an extremely superiorbending properties were confirmed. In these test pieces, the hardnessafter aging process was 310 Hv or more, and the tensile strength was1000 MPa or more. TABLE 5 Recrystallization annealing condition AverageCharacteristic before aging process 0.2% Compo- Holding crystal TensileElonga- Electrical Tensile proof Elonga- Electrical Hard- sition timeparticle strength tion Conductivity MBR strength stress tionConductivity ness Evalua- No. wt % (° C.) sec. μm MPa % %IACS /t MPa MPa% %IACS Hv tion 1 2.9Ti-Cu 750 30 3 850 1 3 2 970 900 10 13.7 300Bending inferior 2 2.9Ti-Cu 750 45 5 790 2 4 0 1030 880 17 14.3 315Superior 3 2.9Ti-Cu 750 60 8 785 2 4 0 1035 946 12 12.5 320 Superior 42.9Ti-Cu 750 80 10 770 2 4 0 1030 920 13 13.7 310 Superior 5 2.9Ti-Cu750 120 15 760 1 4 0 1020 920 13 14.1 315 Superior 6 2.9Ti-Cu 750 180 20670 1 5 2 972 854 14 9.5 310 Bending inferior 7 3.0Ti-0.15 770 20 3 8201 2 2 980 870 10 13.7 300 Bending Zr-Cu inferior 8 3.0Ti-0.15 770 40 5780 2 3 0 1015 920 15 14.2 310 Superior Zr-Cu 9 3.0Ti-0.15 770 60 8 7702 3 0 1020 940 15 13.9 315 Superior Zr-Cu 10 3.0Ti-0.15 770 80 10 780 23 0 1010 900 17 14.4 310 Superior Zr-Cu 11 3.0Ti-0.15 770 120 15 760 1 30 1015 900 15 14.0 310 Superior Zr-Cu 12 3.0Ti-0.15 770 150 20 690 1 4 2990 890 17 9.8 300 Bending Zr-Cu inferior

Example 3

[0078] Electrolytic cathode copper or oxygen-free copper, and metal lumpof additive elements or master alloy were used as raw materials, andcopper alloy ingots of various compositions shown in Table 6 (examples)and Table 7 (comparative examples) were melted in a high frequencymelting furnace. Hot tops of these ingots (measuring 50 mm thick×100 mmwide×150 mm long, weighing about 7000 g) were cut off, and afterremoving the surface layer, they were heated for 1 hour or more at 850°C., and the material was hot rolled to a thickness of 8 mm while keepingthe temperature at 600° C. or more, and it was cooled in water. Thematerial temperature in hot rolling was measured by two-color pyrometerpreliminarily compensated for temperature. The surface oxide scale wasremoved by machine polishing in a thickness of about 0.4 mm on one side,and the plate was cold rolled to a specified thickness of less than 0.4mm (working ratio 95% or more), and the material surface was degreasedby an organic solvent such as acetone, and specified aging was processedin a vacuum annealing furnace, and the sample materials were therebyprepared. TABLE 6 Composition and manufacturing conditions of highstrength titanium copper alloys of the invention Manufacturingconditions Hot rolling condition Cold Aging process CompositionMin.material Final- rolling Holding (wt %) temperature thicknessprocessing Temperature time No. Ti Others (° C.) (mm) ratio (%) (° C.)(hr) 1 2.3 — 680 8.0 97 380 6 2 2.6 — 700 8.0 98 380 6 3 2.9 — 730 8.597 380 10 4 3.2 — 700 8.0 97 380 10 5 3.4 — 710 7.5 97 360 6 6 3.5 — 7308.0 97 360 6 7 2.9 Zn1.0, 700 8.0 97 400 6 Fe0.20 8 2.6 Sn0.21 700 8.598 380 6 9 2.5 Cr0.10 710 7.5 96 420 6 10 3.0 Zr0.15 700 7.5 97 380 1011 3.2 Fe0.20 720 8.0 97 360 8 12 2.7 Ni0.30 700 8.0 97 380 6 13 3.2In0.25 680 8.0 97 380 6 14 3.0 Mn0.10 700 8.5 96 380 6 15 3.1 P0.07 7008.5 98 360 8 16 2.8 Si0.13 710 8.0 97 420 6 17 2.7 Zn0.7, 710 8.0 97 4006 Cr0.30, Zr0.15 18 2.9 Zn1.2, 730 8.0 97 380 6 In0.10, Fe0.16, P0.03 193.1 Sn0.15, 720 7.5 96 420 6 P0.15 20 2.6 Mn0.15, 700 7.5 99 360 4 P0.1021 2.9 Zn0.8, 740 8.0 97 360 8 Ni0.25, Si0.05 22 3.3 Zn1.1, 750 8.0 97380 10 Cr0.15, Zr0.05, Mn0.05 23 3.2 Zn0.1, 710 8.0 97 380 6 Ni0.25,Sn0.15

[0079] TABLE 7 Composition and manufacturing conditions of alloys ofcomparative examples Manufacturing conditions Hot rolling condition ColdAging process Composition Min.material Final- rolling Holding (wt %)temperature thickness processing Temperature time No. Ti Others (° C.)(mm) ratio (%) (° C.) (hr) 24 1.5 — 680 8.0 97 420 6 25 0.009 Zn1.5, 6808.0 97 420 6 Cr0.30, Zr0.15 26 5.5 Ni0.50, 720 35 *) Cracked during hotrolling P0.15 27 4.0 Zn0.5, 720 8.5 *) Cracked during cold rollingNi1.20, Si0.50 28 2.8 Zn4.2, 700 8.0 96 380 6 Ni1.30, Si0.40 29 3.1Zn1.5, 700 8.0 96 380 6 Ni1.50, Sn1.10, P0.30 30 3.0 — 580 25 *) Crackedduring hot rolling 31 2.9 Zn1.5 580 15 *) Cracked during cold rolling 323.2 — 700 10 85 360 6 33 2.7 Zn1.0, 720 10 90 360 6 In0.30, P0.15 34 3.1Zn1.5, 700 8.0 97 200 6 Fe0.35, Mn0.15 35 3.1 Zn1.8, 700 8.0 96 450 50Sn0.50 36 3.0 — 700 8.5 98 650 0.5 37 2.9 — 720 8.5 98 450 0.5 38 2.8 —750 8.0 96 200 50 39 2.9 — 730 8.5 97 — — 40 3.2 — 700 8.0 97 — —

[0080] From the sheet obtained in this manufacturing process, varioustest pieces were sampled, and were subjected to material tests. Thestrength was evaluated by the tensile test according to JIS Z 2241, andthe 0.2% proof stress, tensile strength, and elongation were evaluated.The test pieces were No. 13B type test pieces conforming to JIS Z 2201.The electrical conductivity was measured according to JIS H 0505.Results of measurements are shown in Tables 8 and 9. TABLE 8 Evaluationof high strength titanium copper alloys of the invention Tensile 0.2%proof Electrical strength stress Elonga- Conductivity Evalua- No. (MPa)(MPa) tion (% IACS) tion 1 1230 1180 3 10.2 Superior 2 1270 1220 3 11.3Superior 3 1290 1240 2 11.2 Superior 4 1310 1260 2 10.3 Superior 5 13001220 2 11.4 Superior 6 1310 1240 2 10.3 Superior 7 1290 1220 3 11.5Superior 8 1300 1250 3 10.4 Superior 9 1260 1200 4 10.3 Superior 10 12801220 3 11.7 Superior 11 1270 1200 2 11.2 Superior 12 1250 1180 4 12.3Superior 13 1290 1210 3 12.2 Superior 14 1280 1230 3 11.1 Superior 151310 1250 2 10.0 Superior 16 1270 1210 3 11.1 Superior 17 1280 1210 312.0 Superior 18 1290 1230 2 10.8 Superior 19 1260 1200 4 11.6 Superior20 1300 1240 3 10.4 Superior 21 1280 1220 3 12.1 Superior 22 1280 1230 212.0 Superior 23 1270 1220 2 11.7 Superior

[0081] TABLE 9 Evaluation of high strength titanium copper alloys ofcomparative examples Tensile 0.2% proof Electrical strength stressElonga- Conductivity No. (MPa) (MPa) tion (% IACS) Evaluation 24 780 7202 26.4 Poor 24 780 720 2 26.4 Poor 25 800 720 2 55.1 Poor 26 — — — — Notevaluated 27 — — — — Not evaluated 28 1280 1220 1 8.0 Poor 29 1280 12201 7.8 Poor 30 — — — — Not evaluated 31 — — — — Not evaluated 32 11601090 1 10.3 Poor 33 1180 1100 1 10.1 Poor 34 1210 1100 1 5.7 Poor 351040 940 2 13.2 Poor 36 1060 1000 1 13.1 Poor 37 1250 1160 1 8.0 Poor 381230 1130 1 5.8 Poor 39 1220 1120 1 6.0 Poor 40 1250 1160 2 5.8 Poor

[0082] All examples of the invention in Table 8 recorded a tensilestrength of 1200 MPa or more as required in a fork-shaped connector, andin particular, examples Nos. 4 to 6, 8, 15, and 20 exhibited a tensilestrength of 1300 MPa or more. However, in the comparative examples shownin Table 9, No. 26, 27, 30, and 31 cracked during hot or cold rolling,and the manufacturing efficiency was poor, and the characteristicsthereof could not be evaluated. That is, No. 26 and 27 were too high inTi content, and No. 26 cracked in hot rolling, and although hot rolledto a thickness of 35 mm, subsequent processing was not continued. No. 27did not crack in hot rolling; however, edge cracking occurred in thesubsequent cold rolling. No. 30 and 31 were low in aging temperature,and the temperature was below 600° C. at a thickness of 25 mm and 15 mm,respectively, and edge cracking occurred in cold rolling after hotrolling.

[0083] No. 24 is low in Ti content, and it is hence low in strength. No.25 is also low in Ti content, and it is an example of a Cu—Cr—Zr copperalloy, and although the electrical conductivity is high, the strength islow. No. 28 and 29 are high in contents of Zn and others, and theelectrical conductivity is low, and No. 29 formed edge cracking duringcold rolling.

[0084] No. 32 and 33 are too low in workability of cold rolling, and thestrength is low. No. 34 and 38 are low in aging temperature, and inspite of a long aging period of 50 hours for No. 38, desired electricalconductivity is not achieved. No. 37 has a short aging period, anddesired electrical conductivity is not achieved. Nos. 35 and 36 are highin aging temperature or have long aging periods, and also because theworking ratio of cold rolling before the aging process is high, itresults in over-aging, and high strength is not obtained.

[0085] Nos. 39 and 40 are similar to alloys of Nos. 3 and 4 of theinvention manufactured in the same process up to cold rolling, but arenot aged, and although a high strength of 1200 MPa or more is obtainedby cold rolling at high working ratio, the electrical conductivity islow, and they cannot be used in fork-shaped connector.

[0086] Thus, the titanium copper of the invention can be obtained onlyby the manufacturing method of the invention, and it is a titaniumcopper alloy having a tensile strength of 1200 MPa or more and anelectrical conductivity of 10% IACS or more, not obtainable in theconventional art. The fork-shaped connector using the high strengthtitanium copper of the invention has a contact pressure equivalent tothat of beryllium copper.

Example 4

[0087] Of the materials manufactured up to the cold rolling processingin Table 6 in example 3, those listed in Table 10 were selected andpress worked. These press worked test pieces were aged in the samecondition as in example 3. Characteristics of test pieces wereinvestigated before and after the aging process in the same method as inexample 3, and the results are recorded in Table 10. To evaluate thethermal expansion and shrinkage rate, a test piece of 100 mm×10 mm wascut out in a parallel direction to rolling direction, the distancebetween specified marking positions was measured by using athree-dimensional coordinate measuring apparatus, and the markingposition distance was measured again after the aging process, and thedimension change rate was determined from the measurements before andafter heating. By way of comparison, using the material shown in Table 7and beryllium copper, test pieces were prepared under the same conditionaforementioned, and the characteristics were measured in the samemethod. The results are shown in Table 10. TABLE 10 Evaluation of highstrength titanium copper alloys of the invention Characteristic beforeaging process Characteristic after aging process Thermal Composi-Tensile Elonga- Electrical Tensile 0.2% proof Elonga- Electrical Hard-expansion/ tion strength tion Conductivity strength stress tionConductivity ness shrinkage Evalua- No. wt % MPa % %IACS MPa MPa % %IACSHv % tion 1 2.3Ti 1100 2 7 1230 1180 3 10 350 0.06 Superior 2 2.9Ti 11702 7 1290 1240 2 11 360 0.05 Superior 3 3.4Ti 1180 1 5 1300 1220 2 11 3700.05 Superior 4 2.9Ti- 1160 1 5 1290 1220 3 12 360 0.06 Superior 1.0Zn-0.2Fe 5 2.5Ti- 1140 2 6 1260 1200 4 10 350 0.06 Superior 0.10Cr 6 3.2Ti-1150 1 5 1270 1200 2 11 350 0.06 Superior 0.20Fe 7 3.2Ti- 1160 1 5 12901210 3 12 360 0.06 Superior 0.25In 8 3.1Ti- 1180 2 4 1310 1250 2 10 370.05 Superior 0.07P 9 3.1Ti- 1140 1 5 1260 1200 4 12 350 0.06 Superior0.15Sn- 0.10P 10 2.9Ti- 1160 2 4 1280 1220 3 12 350 0.05 Superior 0.8Zn-0.25Ni- 0.05Sn 11 1.5Ti 650 3 7 780 720 2 26 250 0.04 Poor 12 2.8Ti-1140 1 3 1280 1220 1 8 340 0.05 Poor 4.2Zn- 1.30Ni- 0.40Sn 13 2.7Ti-1060 1 5 1180 1100 1 10 320 0.04 Poor 1.0Zn- 0.30In- 0.15P 14 3.1Ti-1170 2 3 1210 1100 1 6 320 0.05 Poor 1.5Zn- 0.35Fe- 0.15Mn 15 3.1Ti- 9802 5 1040 940 2 13 310 0.05 Poor 1.8Zn- 0.50Sn 16 1.9Be- 560 15 16 13001200 3 25 380 0.11 Shrinkage 0.25Co- inferior Cu

[0088] As can be seen from Table 10, in Nos. 1 to 10 in example 4, thestrength after the aging process was equivalent to that of berylliumcopper (No. 16), and a high electrical conductivity was obtained. Incontrast, with No. 11, the titanium content was less than 2.0% by mass,and the tensile strength was low. In No. 16, the thermal expansion andshrinkage rates were extremely large.

[0089] According to the invention, as described herein, the titaniumcopper alloy is increased in strength without sacrificing the bendingproperties, and the required characteristics as the terminal connectorfor electronic component can be improved, so that a material for aterminal connector of high reliability can be presented. In the examplesof the invention, the titanium copper alloy has a tensile strength of1200 MPa or more and an electrical conductivity of 10% IACS, and it isincreased in strength to a level equal to that of beryllium copper, andit is improved so as to be a copper alloy suited for use in terminalconnectors for electronic component, in particular, for fork-shapedconnector for FPCs, and it is shown to be usable sufficiently as asubstitute copper alloy for beryllium copper alloy. IN addition, if thecontact of the terminal connector is plated before or after working, thestrength is hardly changed, and the effects of the invention areunchanged.

What is claimed is:
 1. A high strength titanium copper alloy consistingof Ti at 2.0% by mass or more to 3.5% by mass or less; the balance ofcopper and inevitable impurities; and the average grain size of 20 μm orless; the alloy further comprising a 0.2% proof stress expressed by “b”of 800 N/mm² or more; and a bending radius ratio (bending radius/sheetthickness) not causing cracking as expressed by “a” by a W-bending testin a transverse direction to a rolling direction; wherein “a” and “b”satisfy a≦0.05×b−40.
 2. A high strength titanium copper alloy consistingof Ti at 2.0% by mass or more to 3.5% by mass or less; at least one ofZn, Cr, Zr, Fe, Ni, Sn, In, Mn, P, and Si at 0.01% by mass or more to3.0% by mass or less in total; and the balance of copper and inevitableimpurities; the alloy further comprising an average grain size of 20 μmor less; a 0.2% proof stress expressed by “b” of 800 N/mm² or more; anda bending radius ratio (bending radius/sheet thickness) not causingcracking as expressed by “a” by a W-bending test in a transversedirection to a rolling direction; wherein “a” and “b” satisfya≦0.05×b−40.
 3. The high strength titanium copper alloy according toclaim 1, wherein the average grain size is in a range of 3 to 20 μm. 4.The high strength titanium copper alloy according to claim 1, whereinthe titanium copper alloy is obtained by performing finalrecrystallization annealing at a temperature below a borderline of anα-phase and an α+Cu₃Ti phase.
 5. The high strength titanium copper alloyaccording to claim 2, wherein the titanium copper alloy is obtained byperforming final recrystallization annealing at a temperature below aborderline of an α-phase and an α+Cu₃Ti phase.
 6. A manufacturing methodfor a high strength titanium copper alloy according to claim 1,characterized by performing final recrystallization annealing at atemperature below a borderline of an α-phase and an α+Cu₃Ti phase.
 7. Amanufacturing method for a high strength titanium copper alloy accordingto claim 2, characterized by performing final recrystallizationannealing at a temperature below a borderline of an α-phase and anα+Cu₃Ti phase.
 8. The manufacturing method for a high strength titaniumcopper alloy according to claim 6; wherein the alloy is cooled, afterfinal recrystallization annealing, at a cooling rate of 100° C./sec ormore; cold worked at a working ratio of 5 to 70%; and subjected to anaging process for 1 hour or more to 15 hours or less at a temperature of300° C. or more to 600° C. or less.
 9. The manufacturing method for ahigh strength titanium copper alloy according to claim 7; wherein thealloy is cooled, after final recrystallization annealing, at a coolingrate of 100° C./sec or more; cold worked at a working ratio of 5 to 70%;and subjected to an aging process for 1 hour or more to 15 hours or lessat a temperature of 300° C. or more to 600° C. or less.
 10. A terminalconnector using a high strength titanium copper alloy according toclaim
 1. 11. A terminal connector using a high strength titanium copperalloy according to claim
 2. 12. A high strength titanium copper alloywhich is subjected to an aging process after press working, the alloyconsisting of: Ti at 2.0% by mass or more to 3.5% by mass or less; andthe balance of copper and inevitable impurities; the alloy furthercomprising a grain size of 5 to 15 μm; wherein cracking does not occurby a W-bending test in a transverse direction to a rolling directionwith a bending radius of zero before the aging process, and the hardnessof the worked matrix after the aging process is 300 Hv or more.
 13. Ahigh strength titanium copper alloy which is subjected to an agingprocess after press working, the alloy consisting of: Ti at 2.0% by massor more to 3.5% by mass or less; at least one of Zn, Cr, Zr, Fe, Ni, Sn,In, Mn, P, and Si at 0.01% by mass or more to 3.0% by mass or less intotal; and the balance of copper and inevitable impurities; the alloyfurther comprising a grain size of 5 to 15 μm; wherein cracking does notoccur by a W-bending test in a transverse direction to a rollingdirection with a bending radius of zero before the aging process, andthe hardness of the worked matrix after the aging process is 300 Hv ormore.
 14. A manufacturing method for a high strength titanium copperalloy according to claim 12, comprising the steps of: performing finalrecrystallization annealing at a temperature below a borderline of anα-phase and an α+Cu₃Ti phase to adjust the grain size to 5 to 15 μm; andperforming final cold rolling at a working ratio of 5 to 50%.
 15. Amanufacturing method for a high strength titanium copper alloy accordingto claim 13, comprising the steps of: performing final recrystallizationannealing at a temperature below a borderline of an α-phase and anα+Cu₃Ti phase to adjust the grain size to 5 to 15 μm; and performingfinal cold rolling at a working ratio of 5 to 50%.
 16. A terminalconnector using a high strength titanium copper alloy according to claim12.
 17. A terminal connector using a high strength titanium copper alloyaccording to claim
 13. 18. A high strength titanium copper alloyconsisting of: Ti at 2.0% by mass or more to 3.5% by mass or less; andthe balance of copper and inevitable impurities; the alloy furthercomprising a tensile strength of 1200 MPa or more and an electricalconductivity of 10% IACS or more.
 19. A high strength titanium copperalloy consisting of: Ti at 2.0% by mass or more to 3.5% by mass or less;Zn at 0.05% by mass or more to 2.0% by mass or less; at least one of Cr,Zr, Fe, Ni, Sn, In, Mn, P, and Si at 0.01% by mass or more to 3.0% bymass or less in total; and the balance of copper and inevitableimpurities; the alloy further comprising a tensile strength of 1200 MPaor more and an electrical conductivity of 10% IACS or more.
 20. Amanufacturing method for a high strength titanium copper alloy accordingto claim 18, comprising the steps of: hot rolling at a temperature of600° C. or more; cold rolling successively at a working ratio of 95% ormore; and aging at a temperature of 340° C. or more to less than 480° C.for 1 hour or more to less than 15 hours while maintaining anagglomerated matrix after the cold rolling.
 21. A manufacturing methodfor a high strength titanium copper alloy according to claim 19,comprising the steps of: hot rolling at a temperature of 600° C. ormore; cold rolling successively at a working ratio of 95% or more; andaging at a temperature of 340° C. or more to less than 480° C. for 1hour or more to less than 15 hours while maintaining an agglomeratedmatrix after the cold rolling.
 22. A fork-shaped connector using a highstrength titanium copper alloy according to claim
 18. 23. A fork-shapedconnector using a high strength titanium copper alloy according to claim19.
 24. A high strength titanium copper alloy which is subjected to anaging process after press working, the alloy consisting of: Ti at 2.0%by mass or more to 3.5% by mass or less; and the balance of copper andinevitable impurities; the alloy further comprising a worked matrixhaving a hardness of 345 Hv or more after the aging process.
 25. A highstrength titanium copper alloy which is subjected to an aging processafter press working, the alloy consisting of: Ti at 2.0% by mass or moreto 3.5% by mass or less; Zn at 0.05% by mass or more to 2.0% by mass orless; at least one of Cr, Zr, Fe, Ni, Sn, In, Mn, P, and Si at 0.01% bymass or more to 3.0% by mass or less in total; and the balance of copperand inevitable impurities; the alloy further comprising a worked matrixhaving a hardness of 345 Hv or more after the aging process.
 26. Amanufacturing method for a high strength titanium copper alloy accordingto claim 24, comprising the steps of: hot rolling at a temperature of600° C. or more; and cold rolling successively at a working ratio of 95%or more.
 27. A manufacturing method for a high strength titanium copperalloy according to claim 25, comprising the steps of: hot rolling at atemperature of 600° C. or more; and cold rolling successively at aworking ratio of 95% or more.
 28. A fork-shaped connector using a highstrength titanium copper alloy according to claim
 24. 29. A fork-shapedconnector using a high strength titanium copper alloy according to claim25.